Researchers have identified it Tmesipteris oblanceolataa fern from New Caledonia, which has the largest recorded genome, surpassing the previous record holder Paris japonica. This discovery, described in the iScience magazine, reveals that this fern contains more than 50 times more DNA than humans and highlights the significant implications that larger genomes have for plant biology and adaptation. Credit: SciTechDaily.com
The Tmesipteris oblanceolata fern sets a new record for the largest genome, impacting plant growth and adaptation insights.
- A New Caledonian fern kind awarded 3 Guinness World Records titles; Largest plant genome, largest genome and largest fern genome by quantity DNA in the core
- Vast, the Tmesipteris oblanceolata genome is bigger than the Big Ben tower in London
- Discovery raises new questions about how much DNA can be stored in cells
- Study will help scientists understand how genome size affects species in the face of biodiversity loss and climate change
A record-breaking genome
A new record holder has been discovered for the largest amount of DNA stored in the nucleus of any living organism on Earth. The details were presented in a new study published in the journal iScience on May 31 by researchers from the Royal Botanic Gardens, Kew, and the Institut Botànic de Barcelona (IBB-CSIC) in Spain.
The New Caledonian fork fern species Tmesipteris oblanceolata was found to contain more than 100 meters of unraveled DNA and more than 50 times more DNA than humans. He has thus dethroned the Japanese flowering plant species Paris japonica, which has held this record since 2010. In addition, the plant has achieved three Guinness World Records titles for the largest plant genome, the largest genome and the largest fern genome for the amount of DNA in its nucleus.
A study shows that Tmesipteris oblanceolata has the largest genome, offering new perspectives on plant evolution and challenges. Credit: Kew
The fern’s natural habitat and study methodology
T. oblanceolata is a rare species of fern found on the island of New Caledonia, an overseas French territory located in the southwestern Pacific Ocean, about 750 miles east of Australia, and some of its neighboring islands such as Vanuatu. The genus Tmesipteris is a little-studied group of plants consisting of approximately 15 species, most of which occur on a range of islands in the Pacific and Oceania.
So far, scientists have only estimated the size of the genomes of two species of Tmesipteris: T. tannensis And T. oblique – both were found to contain gigantic genomes, 73.19 and 147.29 gigabase pairs (Gbp) respectively.
In 2023, lead authors Dr. Jaume Pellicer and Dr. Oriane Hidalgo, from the IBB and formerly of RBG Kew, to New Caledonia to collect samples of Tmesipteris, which were then analyzed to estimate the size of their genomes. This involved isolating the nuclei of thousands of cells, staining them with a dye, and then measuring how much dye had bound to the DNA in each nucleus – the more dye, the larger the genome.
Groundbreaking findings and comparisons
The analysis revealed the species T. oblanceolata have a record-breaking genome size of 160.45 Gbp, which is approximately seven percent larger than that of P. japonica (£148.89).
When the DNA from each cell of this fern is unraveled, it would be taller than the Elizabeth Tower in Westminster, London, which stands 96 meters tall and is home to the world-famous Big Ben clock. By comparison, the human genome contains about 3.1 Gbp spread over 23 chromosomes, and when stretched like a ball of yarn, the length of DNA in each cell measures only about 2 meters.
Implications of genome size for plant biology
Dr. Pellicer, a researcher in evolutionary biology, says: “Tmesipteris is a unique and fascinating small genus of ferns, whose ancestors evolved about 350 million years ago – long before dinosaurs set foot on Earth – and it is distinguished by its mainly epiphytic habit. [it grows mainly on the trunks and branches of trees] and limited distribution in Oceania and several Pacific Islands. For a long time we thought that breaking the previous size record of the Parisian japonica would be an impossible mission, but once again the limits of biology have surpassed our most optimistic predictions.
“Based on our previous research, we anticipated the existence of giant genomes in Tmesipteris. That said, the discovery of the largest genome of all is not just a feat of scientific research, but the culmination of a nearly fourteen-year journey into the limitless complexity and diversity of plant genomes.”
To date, scientists around the world have estimated the genome sizes of more than 20,000 eukaryotic organisms, revealing a wide range of genome sizes across the tree of life. These in turn appear to have a profound impact not only on their anatomy, as larger genomes require larger cells to house them and take longer to replicate, but also on the way they function, evolve and where and how they to live.
In animals, some of the largest genomes include the marbled lungfish (Protopterus aethiopicus) at 129.90 Gbp and the Neuse River water dog (Necturus lewisi) at 117.47 Gbp. In stark contrast, six of the largest known eukaryotic genomes are held by plants, including the European mistletoe (Viscum album) with a volume of 100.84 Gbp.
Surprisingly, having a larger genome is usually not an advantage. In the case of plants, species that possess large amounts of DNA are restricted to slow-growing perennials and are less efficient at doing so photosynthesis (the process by which plants convert the sun’s energy into sugars) and require more nutrients (especially nitrogen and phosphates) to grow and compete successfully with their smaller-genome neighbors. Such effects can in turn affect a plant’s ability to adapt to climate change and its risk of extinction.
Reflections on genome diversity and future research
Dr. Ilia Leitch, Senior Research Leader – Character Evolution at RBG Kew, said: “Who would have thought that this small, unassuming plant that most people would probably walk past without notice could have a world record for genome size. Compared to other organisms, plants are incredibly diverse when viewed at the DNA level, and that should make us think about their intrinsic value in the broader picture of global biodiversity. This discovery also raises many new and exciting questions about the upper limits of what is biologically possible, and we hope to one day solve these mysteries.”
Adam Millward, Managing Editor of Guinness World Records, says: “To think that this innocent-looking fern contains fifty times more DNA than humans is a humbling reminder that there is still so much about the plant kingdom we don’t know, and that record holders are not always the flashiest on the outside.
Reference: “A 160 Gbp fork fern genome shatters the size record for eukaryotes” by Pol Fernández, Rémy Amice, David Bruy, Maarten JM Christenhusz, Ilia J. Leitch, Andrew L. Leitch, Lisa Pokorny, Oriane Hidalgo and Jaume Pellicer, May 31, 2024 , iScience.
DOI: 10.1016/j.isci.2024.109889
The study into the genome size of Tmesipteris oblanceolata was carried out by an international team of researchers from the Royal Botanic Gardens Kew, Queen Mary University of London, the Herbarium of New Caledonia and the Spanish Research Council (CSIC).